Pressed collector



July 28, 1931. A. wRNx-:R v1,816,629

PREssED COLLECTOR Filed March 16, 1929 Patented July 28, 1931 FFHCEANTON WRNER, OF VAIHINGEN-ON-'IE-FXLDEBN, GERMANY PRESSE@ COLLECTORApplication led March 1G, 1929, Serial No.

The present invention relates to commutators of the type in which themeans, securing the copper bars or segments, are embedded in a moldedinsulating composition. The usefulness of this type of commutator islimited, however, since the mechanical properties of the moldedcomposition are insufhcient to take up the various stresses developed bythe centrifugal forces during the rotation of the collector, theconsequences of this stress being increased on account of the heat whicharises simultaneously with the creation of the said stresses.

The invention eliminates these shortcomings by interposing between thecopper segments and the molded composition a` body adapted to take upthe tensile stresses created within the commutator and to transform theminto compressive forces, which act on the molded composition arrangedbetween the said body and segments.

One embodiment of the invention is illustrated by way of example in theaccompanying drawings, in which Figure l is an axial section of theloosely assembled commutator,

Figure 2 is a front View of the same,

`Figure Q is a fragmentary front view of the commutator, the ligurebeing drawn on a slightly enlarged scale and showing the coinmutatorbefore shrinking of the same sets in.

Figure 2b is a fragmentary sectional front view of the commutator online Ll-l of Fig. 3, the figure being drawn on a slightly enlarged scaleand showing the commutator after shrinking of the same sets in.

' Figure 3 is an axial section of the finished commutator and Figure lis a cross section thereof on thel line 4 4 of Figure 3.

The commutator comprises a copper seg- 347,74, and in Germany December7, 1928.

have the notches d extend from its narrow sides inwardly so that thecopper segments a, as arranged in the commutator, are of a perfect leishape, 2 prongs of the copper segments a extending equidistantly at bothsices.

lnto the lopening formed by notches Z on either side of the commutatoran annular seamless ring, such as an iron ring e, is inserted into eachof said notches, so as to be flush with the outside ends of the coppersegments and to have its inner peripheral face in temporary engagementwith the upper peripheral face of the lower prongs of the coppersegments a. It will further be noted from an inspection of Figure 2 thata space f is still left after the insertion of the iron rings c abovethe same within the notches (Z, a small space is also left at the rearof the rim of each of said rings e. It i-s thus obvious that the rings care not in contact with the upper prongs of the copper segments, norwith the bridge which connects both the upper and the lower prongs ofthe letter H.

It will be also noticed from an inspection of Figure l that the micabars o are inserted between copper segments aand that they rest withtheir lower edge upon the outer peripheral face of the iron ring e.These mica bars are of rectangular' shape.

During the shrinking of the commutator, the copper segments a and themica bars b are forced radially to the inside to suoli an extent thatthe inner peripheral faces of the upper prongs-of the copper segments aapproach somewhat the rings e, but still leave a considerable intersticebetween each other. This has the consequence that the-upperperipheral'faces of the lower prongs move away from the inner peripheralface of the rings c and thus also create an interstice between eachother, whereby all contact between any of the copper segments a andeither ofthe l2 iron rings e is prevented.

It is evident from an inspection of Figure 8 that the spaces fl and f2arranged below and above, respectively, the iron rings within thenotches CZ are practically of the same width. Inasmuch as the mica barsb bear against the outer peripheral face of the rings l e beforeshrinking, Figure 2, it is self-evident that during the shrinkingtowards the center of the commutator a part of the way is obstructed tothe mica bars b and that b y this resistance the inwardly disposed edgeof the mica bars b is deformed all along the width of the rings einsofar that the material is spread outwardly as is noticed from Figure2b.

Vhen the material of the mica bar is pressed towards the center of thecommutator it may travel unhindered in the free space at the rear of therings e so that, according to the Figures 2b and 3, it is protrudingslightly beyond the inner peripheral face of the ring e. Th-e mica barsb hold the iron rings e very firmly in a central position and beingspread or upset, offer a broad support for the iron rings e. Moreover,they are protected against centrifugal displacement because their faceacts like a dove-tail and the latter being firmly embedded in a fillerconsisting` of an insulating composition, which then in any of the usualways is pressed into the skeleton formed by the copper segments a, themica bars b and the iron rings e. The insulating composition forms thehub of the commutator.

The insulating composition f fills up the intervening spaces between thecopper segments a, the mica sheets b and the rings c, the interstices f1and f2 and'any other interstice, except the space which later on is tobe filled by the shaft on which the commutator is to rotate during itsoperation. It is thus obvious that each of the copper segments a isinsulated in every direction and particularly from the iron rings earranged within the notches d.

'A commutator constructed according to vthe invention is capable ofwithstanding 20,-

O00 revolutions per minute at 200 centigrade without showing the leastdeformation, because the molded composition is freed completely fromunfavorable tensile forces and need take up only compressive stressesbetween the base of the copper segments a and the rings e, which thecomposition is perfectly capable of doing. Therefore, the commutatorpossesses excellent mechanical properties which exclude the possibilityof deformation. Moreover, it is extremely simple to manufacture, as themica bars l) need not be centered any more during assembly, but centerthemselves by means of the' iron rings e. Furthermore, the otherwise sodisadvantageous shrinking of the mica sheets or other similar insulatingmaterial, owing to heat, does not influence the commutator as to itsfirmness of construction, for theinsulating composition molded into theintervening'spaces g between the copper segments keeps the latterabsolutely in radial direction. Finally I may state that there is someconsiderable saving in the expensive mica sheets,

as the mica bars do not cover the entire height of the copper segments,but extend merely up to the rings e.

An additional advantage is that the shaft bearing hitherto required canbe dispensed with for the reason that the molded composition f arrangedbetween the shaft and the segments u is subjected to compressive forcesonly.

It is further evident that instead of two separate rings only onecentral ring could be provided.

lllhat l claim is:

l. A commutator consisting of electrically conductive segments ofrectangular shape and pr vided with notches extending from the narrowsides .inwardly alongl the middle line, insulator segments, ofrectangular shape and of smalleiI width than aforesaid conductivesegments, havin part of their inner edge spread outwardly, both beingalternately arranged in annular form so as to form a cylinder having anannular groove in each of its front and rear sides, a metal ring in eachof aforesaid grooves being in contact with the outwardly spread inneredge of aforesaid insulator segments and being substantiallyequidistantly disposed from the walls of the notches of said conductivesegments, and an electrically non-conductive iiller provided with anopening` for the shaft.

Q. A commutator consisting of copper segments of rectangular shape andprovided with notches extending from the narrow sides inwardly along themiddle line, mica segments, of rectangular shape and of smaller widththan aforesaid conductive segments, having part of their inner edgespread outwardly, both being alternately arranged in annular form so asto form a cylinder having anv annular groove in each of its front andrear sides, a steel ring in each of aforesaid grooves being in contactwith the outwardly spread inner edge of aforesaid micay segments andbeing substantially equidistantly disposed from the walls of the notchesof said copper segments, and an electrically nonconductive fillerprovided with an opening for the shaft.

3. The method of making commutators, consisting in setting upalternately rectangular copper segments, provided with notches extendingfrom the narrow side's inwardly along the middle line, and ofrectangular insulator segments of smaller width than the coppersegments, in an annular arrangement so as to have all notches on eachnarrow side form an annular groove, arranging a metal ring within eachof aforesaid grooves so as to have their inner walls contact the coppersegments and with their outer walls a part of the inwardly disposed edgeof the insulator segments, causing the annular arrangement of the copperand insulator segments to shrink inwardly thereby creating` an openspace bei tween each side ofthe metal ring and the copper segment andspreading outwardly the insulator segments along the metal ring, andfilling all the aforesaid open spaces in the annular arrangement with anelectrically nonconductive mass.

4. The method of making commutators, consisting in setting upalternately rectangular copper segments, provided with notches extendingfrom the narrow sides inwardly along the middle line, and of rectangularmica segments of smaller width than the copper segments, in an annulararrangement so as to have all notches on each narrow side form anannular groove, arranging a steel ring within each of aforesaid groovesso as to have their inner walls contact the copper segments and withtheir outer walls Contact a part of the inwardly disposed edge of themica segments, causing the annular arrangement of the copper and micasegments to shrink inwardly thereby creating an open space between eachside of the metal ring and the Copper segment and spreadingoutwardly themica segments along the steel ring, and

filling all the aforesaid spaces in the annular arrangement with anelectrically non-conductive mass.

In testimony whereof I affix my signature.

ANTON WRNER.

